I thought it would be implied, but I meant "not always true".
Regarding intelligence, it's an interesting thing. I'm not sure I understand that assuming animals, in particular cetaceans, to be intelligent requires a "big claim". In fact, it's basically a big claim to assume they are not intelligent. Intelligence is a spectrum, and it does indeed seem to be the case that humans, in general, start from one extreme of that spectrum in assuming that all intelligence needs to be proven. For cetaceans, it's a bit mindboggling at this point that people are still surprised by their intelligence.
Cetacean brains are huge and deeply folded. If you simply look at a whale brain versus a human brain, once would guess that the whale brain is from the more intelligent species. Yes, whales are bigger and thus dictate a larger brain to operate, but it isn't clear what that scaling relationship actually is. And whales are well known to be some of the emotionally evolved creatures on Earth, so it continues to surprise me that there is this hidden assumption that they need to be proven to be intelligent. At this point, it would seem the burden of proof should be on those who think they are not intelligent.
In my opinion, part of the bias is in our own unintelligence. For us to consider something intelligent, it seems we require burden of proof such that the "other" intelligence is related back to our own. However, this completely precludes the perspective and perhaps even discovery of there being different intelligences. For example, the part of the brain related to emotional intelligence in whales dwarfs our own, all relative to the rest of the brain. Thus, it might be hard or even impossible for us to understand such emotional intelligence. This is actually where I think the science might be tunnel visioned. There needs to be more thought put into what intelligence actually is such that we might recognize intelligence that isn't like our own.